The need for systems that can deliver a drug at a controlled rate to a variable environment (e.g. gastrointestinal tract) of use over a specified period of time is well established. The use of novel, charged, water insoluble, non-duffusible resinous powders to modulate drug release from osmotically sensitive devices with rate controlling semipermeable walls that are permeable to water and substantially impermeable to dissolved solutes has not been disclosed in the prior art and represents an advance in drug delivery technology and device composition. U.S. Pat. Nos. 3,854,770 and 3,916,899 disclose devices which have semipermeable walls that are permeable to water and substantially impermeable to dissolved drugs and solutes. A passageway through the semipermeable wall, disclosed as a drilled hole, is provided as an exit portal for the drug through the wall. U.S. Pat. Nos. 4,256,108; 4,160,452; 4,200,098 and 4,285,987 disclose devices which contain multiple wall layers, at least one of said walls having a drilled hole for the release of core components through a rate-controlling semipermeable membrane that is substantially impermeable to dissolved drugs and other solutes. The use of charged resins to modulate drug release from the above devices was not disclosed. U.S. Pat. No. 4,221,778 discloses ion-exchange resin drug complexes as delivery devices where the resin and drug carry opposite charges and osmotic factors are not included; drug release is actuated by exchange of the drug with another ion which dislodges the drug from the resin.